Traditionally, the Herald isn’t known to duck a liberal cause when it sees one. Getting rid of Republican representatives is a liberal cause par excellence. It seems to me that their sitting on this is either poor journalism, esprit de corps with a man who is a member of a traditional liberal constituency, or just plain timing (wait until the election when your party is in striking distance, then hit them hard.) Or a combination of one or more of these.
As far as Foley being a homosexual is concerned, the Herald’s editor stated the following:

Given the potentially devastating impact that a false suggestion of pedophilia could have on anyone, not to mention a congressman known to be gay, and lacking any corroborating information, we chose not to do a story.

Homosexuals generally resent their way of life being linked to paedophilia, but that’s implicit in the editor’s statement.